Double fired multi-path process heater



March 1, 1966 P. voN wlEsENTHAI. ETAL 3,237,610

DOUBLE FIRED MULTI-PATH PROCESS HEATER 5 Sheets-Sheet 1 Filed OCT.. 6, 1964 MarCh 1, 1966 P. vom WIESENTHAL ETAL 3,237,610

DOUBLE FIRED MULTI-PATH PROCESS HEATER Filed Oct. 6, 1964 3 Sheets-Sheet 2 Fig IB PETER VON WIESENTHAL ORNEY Mawh 1, 1966 P. voN wlEsENTHAL E'rAl. 3,237,610

DOUBLE FIRED MULTI-PATH PROCESS HEATER 3 Sheets-Sheet 5 Filed Oct. 6, 1964 INVEN-roRs MERBERT L. BER PIETER von wlEsEN'rHAL United States Patent 3,237,610 DOUBLE FIRED MULTI-PATH PROCESS HEATER Peter von Wiesenthal, New York, and Herbert L. Berman,

Jericho, N.Y., assignors to Alcorn Combustion Company, New York, N.Y., a corporation of Delaware Filed Oct. 6, 1964, Ser. No. 401,906 3 Claims. (Cl. 122-240) This disclosure relates to process heaters. The invention contemplates an arrangement suitable for double firing of radiant tubes even with several parallel flow paths through lthe heater.

Fired heaters with several parallel flow paths encounter characteristic design difficulties. Fitting the several flow paths into such a heater can involve complex tube configurations which run up pressure losses and impose a burden on tube costs. Tube costs are especially critical when expensive alloy is employed.

The design here presented solves these difficulties in a novel and interesting manner. Vertical tubes in the radiant coil are mounted in an annular configuration. Additional rows of vertical tubes extend outward from this annular configuration. The radiant tube coil is fired from within the annular configuration and between the rows of outward tubes. By this scheme double liring of all the radiant tubes is achieved and shorter tube lengths become possible.

To provide symmetrical collecting of parallel streams, an outlet manifold is passed through the heater. The outlet manifold is positioned within a refractory-lined shield and the interior of the shield is .opened to the atmosphere for cooling. Accordingly, -the material requirements for the outlet manifold are eased. Further, positioning the outlet manifold above the furnace charnber elevates outlet terminal connections to conform with process requirements of most installations.

It should also be noted that this general tube configuration fits nicely into a Vertical cylindrical heater so that structural economy is promoted and required plot area is minimized.

These and other features will appear more fully from the accompanying drawings wherein:

FIGURES 1A and 1B are overlapping fragmented, cross-sectional elevation views of a heater which embodies the p-resent invention and taken along line lA of FIGURE III and IB of FIGURE II.

FIGURE II is a cross-sectional view taken along line A-A of FIGURES IA and IB.

FIGURE III is a cross-sectional view taken through the radiant furnace chamber of the heater.

FIGURE IV is a partial cross sectional view taken along line IV-IV of FIGURE II showing the crossover arrangement.

In the drawings setting 1 includes oor 2 and wall means shown as vertical cylindrical wall 3 which embraces radiant furnace chamber 4 therewithin. Cylindrical wall 3 is substantially equidistant from a vertical axis.

Each of the radiant tubes is double fired. Radiant coil generally designated 6 comprises a plurality of inward tubes encircling combustion space 7. Radiant coil 6 further com'pirses rows of outward tubes mounted vertically with each row extending outward from the annular tube configuration to define sector-like outer combustion spaces therebetween. No tubes are mounted against wall 3 which is lined with refractory 9 to prevent excessive heat transfer therethrough.

Burners of known design are used. Inner burners 11 penetrate floor Z and introduce -fuel and air for combustion in inner space 7. Outer burners 12 likewise fire in outer combustion spaces 8.

Patented Mar. 1, 1966 It is a primary objective of this design to double fire the radiant tubes and to allow for many parallel flow paths through Ithe heater. Two sets of four parallel flow paths are shown in FIGURES II and IV. In plan, the radiant coil portion of each set of four flow paths takes up a ninety-degree sector. The shown flow paths are typical of the other three ninety-degree (90) sectors so this embodiment has sixteen parallel flow paths in all. Employing the teaching here set forth it should be understood that more or less than sixteen parallel flow paths can be provided. As seen from FIG- URES II and IV a first path starts with inlet header 5 (seen in FIGURE IB) and includes convection tube bank 13, intermediate crossover 14 inward radiant tubes 16 and intermediate crossover 17 to outlet manifold 18. A second path includes downward flow through serpentine convection tube bank 19, intermediate crossover 21, outward radiant tubes 22 and outlet crossover 23 to outlet manifold 18. A third path includes downward flow through serpentine convection tube bank 24, intermediate crossover 26, inward radiant tubes 27 and outlet Crossovers 28 to outlet manifold 18. A fourth path includes downward flow through serpentine convection tube bank 29, intermediate cross-over 31, outward radiant tubes 32 and outlet crossover 33 to outlet manifold 18.

Outlet manifold 18 is close enough to radiant coil 6 convection section 34 to keep crossover lengths small; yet, manifold 18 is external to the heater and is air cooled. These features result from mounting the outlet manifold between radiant furnace chamber 4 and convection section 34. Shield 36 has ends 37 and 38. Setting 1 defines ports 39 and 41. End 37 of the shield is connected in scaled relationship to the setting about port 39. End 38 is connected in sealed relationship to the setting about port 41 so that air is able to circulate through protected space 42 in which outlet manifold 18 lis mounted.

Along i-ts length shield 36 is spaced from wall 3 so that the shield does not prevent exhausting of combustion gases from radiant furnace chamber 4. These combustion gases exit via convection section 34 and a suitable stack.

It will be apparent to those skilled in fired heater design that wide deviations can be made in the details of this disclosed embodiment without departing from the spirit of invention outlined in the claims.

What is claimed is:

1. A fired heater comprising in combination a vertical cylindrical setting which includes a floor and cylindrical wall and defines a radiant furnace chamber therewithin,

the cylindrical wall describing a vertical axis from which it is substantially equidistant,

the vertical axis passing through the furnace chamber,

a radiant coil in the furnace chamber and comprising a plurality of inward tubes mounted vertically to form an annular configuration about the vertical axis,

the radiant coil further comprising at least two rows of outward tubes mounted vertically with each of the rows in a plane which includes the vertical axis,

each of the rows of outward tubes arranged outside the annular configuration,

the inward tubes embracing an inner combustion space,

at least one inner burner penetrating through the floor and communicating in flow series with the inner combustion space to introduce fuel and air for combustion therein,

the rows of outward tubes cooperating with the inward tubes and the cylindrical wall to define at least two outer combustion spaces,

at least one outer burner for each of the outer com- .bustion spaces each penetrating through the floor `and communicating with one of the outer combustion spaces to introduce fuel and air for cornbustion therein so that all of the tubes in the radiant coil are fired from two sides,

the inside of the cylindrical wall lined with refractory to reduce heat flux therethrough,

a shield having a first and a second end and positioned horizontally above the furnace chamber,

the shield defining a protected space therewithin,

the setting defining a first port and a second port,

the first end of the shieldconnected in sealed relationship to the setting about the first -port and the second end of the shield connected in sealed relationship to the setting about the second port so that air from the atmosphere can circulate through the protected space,

along its length the shield spaced from the setting to allow passage of combustion gases around the shield `forexit fromthe furnace chamber,

means for circulating a process fluid through the radiant coil,

an ,outlet manifold in the protected space,

at least one outlet crossover connected in flow series from the radiant coil to the outlet manifold and penetrating through the shield.

2. A fired heater comprising in combination a vertical cylindrical setting which includes a floor ,and a cylindrical wall and defines a radiant furnace chamber therewithin,

the cylindrical wall describing a vertical axis from which it is substantially equidistant,

the vertical axis passing through the furnace chamber,

a radiant coil in the furnace chamber and comprising a plurality of inward tubes mounted vertically to form an annular configuration about the vertical axls,

the radiant coil further comprising at least two rows of outward tubes -mounted vertically with each of the rows in a plane which includes the vertical axis,

`each of the rows of outward tubes arranged outside the annular configuration,

the inward tubes embracing an inner combustion space,

at least one inner burner penetrating through the floor and communicating in fiow series with the inner combustion space to -introduce fuel and air for combustion therein,

the rows -ofoutward tubes cooperating with the inward tubes and the cylindrical wall to define at least two outer combustion spaces,

at least one outer burner for each of the outer combustion spaces each penetrating through the fioor and communicating in fiow series with one of the outer combustion spaces to introduce fuel and air for combustion therein so that all of the tubes in the radiant coil are fired from ltwo sides,

the inside of the cylinder wall lined with refractory to reduce heat flux therethrough,

a shield having a first end and -a second end and positioned horizontally above the furnace chamber,

the shield .defining a protected space therewith,

the setting defining a first port and a second port,

the first end of the shield connected in sealed relationship to the setting about the first port and the second end of the shield connected in sealed relationship to the setting about the second port so that air from the atmosphere can cir-culate through the protected space,

the setting defining a convection section above the shield,

along its length the shield spaced from the setting to allow passage of combustion gases around the shield from the furnace-chamber into the convection section,

fiue means remote from the lfurnace chamber and connected in fiow series with the convection section to exhaust combustion `gases therefrom,

a convection coil comprising tubes and mounted in the convection section,

the convection coil arranged for circulating a process stream through the convection tubes in a first convection flow path and a second convection fiow path each in parallel flow relationship with the other,

the radiant coil arranged for circulating the process stream through the radiant tubes in a first radiant flow path and a second radiantfiow path each in parallel fiow relationship -with the other,

intermediate crossover means for delivering the process stream from the first and Vsecond convection flow paths to the first and second radiant fiow paths respectively,

an outlet manifold mounted in the protected space,

a first and a second outlet crossover each connected between the radiant coil :and the outlet manifold so as to accommodate exit from the first and second radiant fiow paths respectively to the outlet manifold, the first and the second outlet Crossovers each penetrating through .the shield.

3. A fired heater comprising in combination a setting which includes a floor as well as wall means defining a furnace chamber therewithin,

a radiant coil in the furnace chamber and comprising a plurality of tubes mounted vertically, at least one burner penetrating through the setting and cornmunicating with the furnace chamber to introduce fuel and air for combustion therein,

Va shield having a first and a second end and positioned horizontally above the furnace chamber,

the shield embracing a protected space therewithin,

the setting defining a first port and a-second port,

the first end of the shield connected in sealed relationship to the setting about the first port and the second end of the shield connected in sealed relationship to the setting about the second port so that atmospheric air can circulate through .the protected space,

the shield along its length spaced from the wall means to allow passage of combustion gases around the shield for exit from the furnace chamber,

means for circulating a process fiuid through the radiant coil,

an outlet manifold mounted in the protected space,

at least one outlet crossover connected in flow series from the radiant coil to the outlet manifold.

References Cited by the Examiner UNITED STATES PATENTS CHARLES I. MYHRE, Primary Examiner. 

3. A FIRED HEATER COMPRISING IN COMBINATION A SETTING WHICH INCLUDES A FLOOR AS WELL AS WALL MEANS DEFINING A FURNACE CHAMBER THEREWITHIN, A RADIANT COIL IN THE FURNACE CHAMBER AND COMPRISING A PLURALITY OF TUBES MOUNTED VERTICALLY, AT LEAST ONE BURNER PENETRATING THROUGH THE SETTING AND COMMUNICATING WITH THE FURNACE CHAMBER TO INTRODUCE FUEL AND AIR FOR COMBUSTION THEREIN, A SHIELD HAVING A FIRST AND A SECOND END AND POSITIONED HORIZONTALLY ABOVE THE FURNACE CHAMBER, THE SHIELD EMBRACING A PROTECTED SPACE THEREWITHIN, THE SETTING DEFINING A FIRST PORT AND A SECOND PORT, THE FIRST END OF THE SHIELD CONNECTED IN SEALED RELATIONSHIP TO THE SETTING ABOUT THE FIRST PORT AND THE SECOND END OF THE SHIELD CONNECTED IN SEALED RELATIONSHIP TO THE SETTING ABOUT THE SECOND PORT SO THAT ATMOSPHERIC AIR CAN CIRCULATE THROUGH THE PROTECTED SPACE, THE SHIELD ALONG ITS LENGTH SPACED FROM THE WALL MEANS TO ALLOW PASSAGE OF COMBUSTION GASES AROUND THE SHIELD FOR EXIT FROM THE FURNACE CHAMBER, MEANS FOR CIRCULATING A PROCESS FLUID THROUGH THE RADIANT COIL, AN OUTLET MANIFOLD MOUNTED IN THE PROTECTED SPACE, AT LEAST ONE OUTLET CROSSOVER CONNECTED IN FLOW SERIES FROM THE RADIANT COIL TO THE OUTLET MANIFOLD. 